Ajmal is due to arrive on Tuesday, June 2 and will be available for at least five weeks until July 7 after the Pears secured approval from the Pakistan Cricket Board.
The spinner could remain with the county for longer if he is not selected by the PCB for Pakistan’s ODI’s with Sri Lanka later this summer.
Ajmal’s first game of his new spell is set to be the NatWest T20 Blast match against Northants Steelbacks at Northampton on Friday, June 5.
He picked up 63 wickets in nine Championship games last summer and his remodelled action gained ICC approval earlier this year.
Director of Cricket Steve Rhodes said: “I’m delighted Saeed is back playing. What he has produced, previous to his problems, was exceptional for us as well as his country.
“We are very optimistic he will do well again for us and obviously he is a feared opponent by all of our opposition in all formats of cricket,” he added.
As well as eight NatWest T20 Blast matches, Ajmal will also be available for three LV= County Championship games; at home against Warwickshire and the trips to Middlesex and Nottinghamshire.
Chief Executive David Leatherdale said: “Saeed, now that Pakistan have issued the No Objection Certificate, is due to arrive on June 2.
“He will certainly be available until July 7 and possibly, depending on selection for Sri Lanka, even longer.
“And, if he wasn’t selected for the Sri Lankan one-dayers, he could be here for the whole summer,” he added.